The present invention relates to a developer solution for a photoresist. More specifically, the present invention relates to a photoresist developer that reduces toppling of the photoresist during later processing and a method of using same.
Photolithographic patterning is a well established technology in the manufacturing processes of various kinds of semiconductor devices and liquid crystal display panels. In this process, prior to etching or diffusion of a substrate surface that surface is electively protected, by coating with a photosensitive resist composition to form a photoresist layer. The photoresist is a light-sensitive liquid that is spread as a uniform thin film on a wafer or substrate. The photoresist layer is pattern-wise exposed to actinic rays such as ultraviolet light, deep ultraviolet light, excimer laser beams, X-rays and electron beams. After the photoresist layer has been exposed to the actinic rays, a developer solution is applied to the resist layer to pattern-wise dissolve away the resist layer. The photoresist material remaining after development shields or masks the regions of the wafer from subsequent etch or implant operations.
The development process of photoresist is performed in order to provide the pattern which will serve as a mask for etching, ion-implantation, lift-off, etc., on the wafer. One of the goals of an effective development process is to minimize pattern distortion. Pattern distortion can be caused by many sources; however, one of the primary sources is surface tension. Surface tension pulls down the walls (i.e., vertical thickness) of the photoresist, also known as toppling, during the rinsing and drying steps of the development process, thereby, destructing the pattern that was originally formed. As shown in FIG. 1, for example, the fine lines used to pattern electrical connections onto a blanket metal are formed by photoresist. When the walls of the photoresist topple, the connections cannot be properly placed onto the blanket metal. Toppling of the photoresist causes much difficulty, is costly as substrates must be scrapped, and time consuming. Accordingly, there is a need for a photoresist developer that will reduce or eliminate the toppling of the photoresist, thereby improving manufacturing efficiency and product yields.
This need is met by the present invention wherein a developer solution is provided that reduces or eliminates the toppling experienced during photoresist development with prior art compositions. In accordance with one embodiment of the present invention, a photoresist developer solution to reduce toppling is provided. The developer solution comprises from about 80% to about 99% of a polyhydric alcohol, from about 0.1% to about 10% of a base compound, and from about 0.001% to about 1.0% of a surfactant. Water may be added as the balance of the solution. The polyhydric alcohol is selected from the group consisting of propylene glycol and ethylene glycol. The base compound can be any Lewis or Bronstead-Lowry base. Preferably, the base compound is tetramethylammonium hydroxide. The surfactant is selected from the group consisting of anionic, cationic, or nonionic.
In accordance with another embodiment of the present invention, a photoresist developer solution to reduce toppling is provided. The developer solution comprises from about 94% to about 99% of a polyhydric alcohol, from about 0.2% to about 5% of a base compound, and from about 0.001% to about 0.010% of a surfactant. Water may be added as the balance of the solution. The polyhydric alcohol is selected from the group consisting of propylene glycol and ethylene glycol. Typically, the base compound is tetramethylammonium hydroxide. The surfactant is selected from the group consisting of anionic, cationic, or nonionic.
In accordance with yet another embodiment of the present invention, a method of patterning a photoresist having reduced tendency to topple is provided. The method comprises applying a photoresist to a substrate, selectively exposing the photoresist to actinic radiation to form an exposed photoresist, and developing the exposed photoresist with a developer solution to provide a photoresist pattern; wherein the developer solution comprises from about 80% to about 99% of a polyhydric alcohol, from about 0. 1% to about 10% of a base compound, and from about 0.001% to about 1.0% of a surfactant. The balance of the solution may be water. The polyhydric alcohol is selected from the group consisting of propylene glycol and ethylene glycol. Typically, the base compound is tetramethylammonium hydroxide. The surfactant is selected from the group consisting of anionic, cationic, or nonionic. The method may also include the steps of rinsing the developed photoresist and drying the developed photoresist.
In accordance with another embodiment of the present invention, a method of patterning a photoresist is provided. The method comprises applying a photoresist to a substrate, selectively exposing the photoresist to actinic radiation to form an exposed photoresist, and developing the exposed photoresist with a developer solution to provide a photoresist pattern; wherein the developer solution comprises from about 94% to about 99% of a polyhydric alcohol, from about 0.2% to about 5% of a base compound, and from about 0.001% to about 0.10% of a surfactant. The balance of the solution may be water. The polyhydric alcohol is selected from the group consisting of propylene glycol and ethylene glycol. Preferably, the base compound is tetramethylammonium hydroxide. The surfactant is selected from the group consisting of anionic, cationic, or nonionic. The method may also include the steps of rinsing the photoresist pattern and drying the photoresist pattern.
Accordingly it is a feature of the present invention to provide a developer solution that will reduce or eliminate toppling of the photoresist. Other features and advantages of the present invention will be apparent in light of the description of the invention embodied herein.